Alternative / non-"boutique" transformers

Ok, just to make it clear right off the bat - i AM somewhat skeptical about the "magic mojo" some of the, let's face it, quite expensive transformers out there, are supposed to have. That, AND i'm a bit of a cheapskate (at times) ;D  So, just for kicks, i browsed through the inventory of some of the bigger electronics retailers, in the audio transformers section.

I'm primarily interested in stuff available in Europe, because long and expensive shipping isn't my thing Not to mention customs fees. Farnell's stock isn't exactly abundant (or cheap), but on the other hand, i've found a few interesting-looking choices in RS's stock.

7.5k:12R (25:1 turns ratio) http://fi.rsdelivers.com/product/triad-magnetics/sp-48/transformer-pc-audiopri7500-ohms-ctsec12-ohms-ctmil-t-27e50mw150vdc/2508972638.aspx
300+300:12.5k+12.5k (1+1:6.45+6.45 turns ratio) http://fi.rsdelivers.com/product/oep/z218a3c/11-to-645645-pcbmount-af-transformer/6676066.aspx
3k:250+250 (3.6:1+1 turns ratio) http://fi.rsdelivers.com/product/oep/e187b/pcb-mount-audio-transformer-250-%CF%89-500-%CF%89-5mw/2106374.aspx

What are the odds any of these might be (somewhat) suitable for condenser output transformers?

"Mojo" not "mojo". With transformers this is much more complex than with audiophile stuff.
You can measure and see how they different can be.
First of all you should look much more carefully in the datasheets, because your examples aren't suitable for condenser microphone output. Only Z218A3C would be useful, but the result wouldn't be as you expected.
Even not looking for impedances (which is important of course), after you find ratio check the frequency response range!
For misers ebay is good option
If you are patient, you can find good transformers for cheap.
The first thing I recommend are beyerdynamic transformers.
Really great for tube and fet microphones, small size is even advantage in this case. They sound really good.

I'm afraid i'm gonna need a slightly more detailed explanation, the main question being "why"?

Anyway, i'm not pretending to know "everything", but transformers CAN be used in either direction, right? In the case of microphones, the higher-impedance winding(s) go towards the circuitry, and the lower-impedance one(s) to the XLR output.

And why exactly wouldn't "even" the Z218AC3 be suitable? High-Z windings in series, and the low-Z ones in parallel - isn't 150ohms "close enough" to the more usual 200ohms? And it's not like the input impedance of mic preamps is anywhere near standardized... ;D

What results would be "expected", then? And how or why wouldn't / couldn't those be achieved? And do we want a wide frequency response out of our transformers, or a limited one?

I know the frequency graph in the Z218AC3 is nowhere near ruler-flat, but did you look at the scale of the Y-axis? It spans -3dBm to +0.5dBm... Or do we want some (more) roll-off on the high-end?

In theory transformers can be used in either direction, but wire size and current capacity can be different for different uses.  In testing various transformer frontwards/backwards/single-ended/push-pull I sometimes find totally different response profiles for each connection, some not good at all.  It can matter a lot.

Doug gived you good explenation.

For theoretical explanations you will need to find someone else.
Transformers and impedances are still my "achilles heel"
From practice i can post my observations only, that transformers with multiple turns are harder to reverse usage than those with simple primary/secondary windings.
You can be suprised how the frequency response can be changed in reversed mode.
You should much more consider what and how the impedances are reflected from both sides of transformer.
Even if there's  stated 150ohm, that doesn't mean that you will get the proper impedance on the output - it depends (not only) on  what is connected to the  input also.

Khron said:

do we want a wide frequency response out of our transformers, or a limited one?

Click to expand...

I think that each really wants something else
On some applications i prefer coloured transformer response on the other flat as possible

If you will be satisfied from 300Hz-100KHz  or 200Hz-15kHz response it's good to you  ;D

Find few different transformers with similar ratio and compare it in existing circuit.
It will show you much more than a theoretical consideration,

Just for what it is worth: I have tested some stock transformers (10:1) coming out of an Apex 460 or Alctron HT11A, and they are not bad at all! (Although everybody says that you should replace the transformer in those microphones. Well, maybe it is just because they are selling them... )

By that way: I used the OEP (1+1:6.45+6.45 turns ratio) but they were not good in a condenser microphone as output transformer.

I have three 2:1 anyone want to buy?
;D

I found some false statements about transformers in some (let say vintage) microphones, made by person which was the maker of upgrade "hyper great" trannies. It is always some kind of marketing...
Many chinese transformers are really decent but with "upgrade" we can get different results.
It's all about what effect we want to achieve.

I really like RFT transformers (funkwerk Leipzig, Kolleda etc.) in microphones as an "downgrade" option
They can add some really nice "colour", especially to the FET microphones

What about something like this?

http://www.mouser.fi/ProductDetail/Hammond-Manufacturing/145O/?qs=sGAEpiMZZMv0IfuNuy2LUR3ZekLBLGAzwLw%252bkyunpzg%3d

Hammond are a pretty big manufacturer, at least in the (guitar) tube amp magnetics field (ok, pun slightly intended ), but not limited to that. I'd reckon they should have at least half a clue what they're doing

More like this!

https://www.buerklin.com/default.asp?search=pikatron&event=ShowSE%28%29&l=e&ch=31754&suggestion=

Look at microphone transformers!

You have from 1:2 to 1:15 ratio....

Cheers

Good example iprovlek!

Khron - really, datasheet is your friend

Look for pikatron "papers" (earlier mentioned frequnecy response) - 40Hz - 20kHz - this is much more what you looking for.

Well, i will admit, THIS is what i was hoping to get out of this thread: more people & minds = more ideas

My whole point, or idea, was that decent quality does NOT need to be indecently priced ;D And yes, call me a blasphemer if you must, but asking for a couple hundred dollars, for a few grams of laminations and wire (neither of which are made of precious metals) is just... a bit too much - and that's putting it mildly

But yeah, great tip, iprovlek! Those Pikatron ones seem like "just what the doctor ordered" I had heard of the brand before, but only regarding power transformers.

...I highly recommend these 3U Audio GZ-series transformers...I have all the variants in different mic builds and they perform quite excellent...they ship to Europe no problem:

GZT-12 (T14/12:1 style):
http://www.ebay.com/itm/3U-Audio-GZT-12-Output-Transformer-for-Vacuum-Tube-Valve-Condenser-Microphone-/111540701945
GZT-87 (T13/9.5:1 style):
http://www.ebay.com/itm/3U-Audio-GZT-87-Output-Transformer-for-Condenser-Microphone-/111683319855
GZT-47 (BV8/6.5:1 style):
http://www.ebay.com/itm/3U-Audio-GZT-47-Output-Transformer-for-Condenser-Microphone-/111540902642

This manufacturer also offers a very impressive line of affordable microphones, all proprietary designs (no OEM Chinese stuff)...they also manufacture and tune all of their own capsules (K67, K47 and C12):
http://3uaudio.com/
Transformer specs:
http://3uaudio.com/chanpin1.asp?dh=2

Feel free to reach out to their customer service if you're interested in quotes for a quantity order:
[email protected]

Khron said:

My whole point, or idea, was that decent quality does NOT need to be indecently priced ;D And yes, call me a blasphemer if you must, but asking for a couple hundred dollars, for a few grams of laminations and wire (neither of which are made of precious metals) is just... a bit too much - and that's putting it mildly

Click to expand...

Some laminations and wire cost pennies, for sure. The overhead in staffing and / or machine costs, and all the other costs of running a business - not a hobby - but a business add a lot to the price. The development costs add a lot to the price. Producing something to a consistent standard adds a lot to the price. Producing a transformer that works in circuit from 20 Hz or below to 20kHz or above (100k, 200k?) while staying flat is not easy. The Hammond example above is 150Hz to 15kHz.

In a microphone, with goodness knows how many dBs of gain after it, you're really going to want some shielding on that transformer too. The Hammond is unshielded. Mu-metal isn't cheap. Forming and annealing mu-metal isn't cheap. Making products for a tiny market like high quality audio recording means low volumes. Low volumes means more expensive everything.

I get your point though. There is certainly a little extra mark-up in transformers which are "clones" of historical models which we all know and love. So there are better deals out there, quality per cost. But you still won't get a really good quality microphone transformer for cheap unless it is second hand. Funked up character transformer, yes, you can find that for cheap.

I use those Pikatron in my G7 and my Elam...

And they are not expensive, more acceptable....

And sound good!

Cheers

Another transformer-related question, which i didn't think warrants a whole new topic:

Apart from the obvious extra level attenuation, would there be any harm in using, say, a 10:1 output transformer in a circuit designed to use a 4-6:1 transformer? In a solid-state circuit, not a tube-based one.

I just read this thread for the first time and noticed Dennis Stone was here (reply #12).

I still can't believe he's gone.

Carry on.

Khron said:

Another transformer-related question, which i didn't think warrants a whole new topic:

Apart from the obvious extra level attenuation, would there be any harm in using, say, a 10:1 output transformer in a circuit designed to use a 4-6:1 transformer? In a solid-state circuit, not a tube-based one.

Click to expand...

What is the microphone model and hwat exact ratio of transformer is?
Could give some exmple?

For example, the JFET + PNP combo that's normal in mics like the sE 2200A - that one has a 4:1 ratio transformer.
I was just wondering what's the worst thing that could happen if that got replaced with something like a Neutrik NTE10/3 (apart from the level reduction).